Append an element to the list if no other element after it is the same as it

Question

x = "haaiiillll"
y=list(x)
z=[]
a=len(y)
n=0
for i in y:
    print(y[n:])
    if i != y[n:]:
        z.append(i)
        n+=1
print(z)

How do I implement this, I can't understand. I have tried to implement a program where it checks if the value with i is there anywhere in the list y if not it will add it otherwise it shouldn't.

So you want to append only if the element is not in the list? — Mahendra Gunawardena, Jul 18 '21 at 13:44
To confirm it - can you show your expected output in this case? For example, given the sample input, is that expected - `h` only, or others? — Daniel Hao, Jul 18 '21 at 14:03
Is trying to create a list like ' hail', remove the duplicates — Mahendra Gunawardena, Jul 18 '21 at 14:25

S.B · Answer 1 · 2021-07-18T14:27:30.720

1

This is the simplest way of doing it and works well for lists which aren't very huge:

x = "haaiiillll"
res = [item for i, item in enumerate(x) if x.find(item, i + 1) == -1]
print(res)

output :

['h', 'a', 'i', 'l']

Using .find() we can see if there is any other values equal to item from it's position until the end. (second parameter in find is the starting point)

edited Jul 18 '21 at 14:27

answered Jul 18 '21 at 14:05

S.B

13,077
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It works, but prob. not very efficient given a long input string? – Daniel Hao Jul 18 '21 at 14:07
1

@DanielHao you're right, I will mention it in answer. – S.B Jul 18 '21 at 14:28

score 1 · Answer 2 · answered Jul 18 '21 at 14:09

As far as I understood, you need to add the element nf the final list only if it appears once in the input list. So, Change the value of n to 1. Keep a set to track whether the element is already seen. And change the condition to check whether the element is in the rest of the list and not seen already.

    n=1
    seen = set()
    for i in y:
        if i not in y[n:] and i not in seen:
            z.append(i)
        seen.add(i)
        n+=1

You problem will be solved.

score 0 · Answer 3 · answered Jul 18 '21 at 13:48

0

if not your_element in your_list:
    your_list.append(your_element)

This way, an element will be added to the list only if it isn't in the list.

answered Jul 18 '21 at 13:48

PRO

169
5

It's not working. why should it be your_list because that's the list I am already going through – Aviral Jul 18 '21 at 13:54

score 0 · Answer 4 · answered Jul 18 '21 at 13:59

0

In the list z there will be only elements different from each other:

x = "haaiiillll"
y=list(x)
z=[]
a=len(y)
n=0
for i in y:
    if i not in z:
        z.append(i)
print(z)

answered Jul 18 '21 at 13:59

SAL

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Append an element to the list if no other element after it is the same as it

4 Answers4